Galapagos History

The giant tortoises of the Galápagos Islands are famous for their impressive size (some weigh over 500 pounds) and their long life spans (averaging more than 100 years). They also played a pivotal role in inspiring the English naturalist Charles Darwin to develop his groundbreaking theory of evolution and natural selection after an eye-opening visit to the Galápagos in 1835. Though scientists think there were once at least eight species of Galápagos tortoise, at least three of these are believed to have gone extinct, including those native to Pinta Island and Floreana Island. Recently, however, scientists discovered that some of their relatives still roam the Galápagos, sparking hope that they may be able to bring these departed species back into existence.

In the 16th century, as many as 250, 000 giant tortoises are believed to have roamed the Galápagos, an archipelago of 19 islands located in the Pacific Ocean some 620 miles (1, 000 km) off the coast of Ecuador. When Spanish explorers stumbled on the islands in 1535, they actually named them for these prehistoric-looking creatures, using an old Spanish world for tortoise (galápago). Hunted as food by pirates, whalers and merchant seamen, more than 100, 000 tortoises were killed over the ensuing three centuries, and by the 1970s only 3, 000 were believed to remain. Of the two primary types of Galápagos tortoises—saddleback and domed—sailors preferred the smaller saddlebacks, who lived at lower elevations and were easier to catch than the domed tortoises; saddleback meat was also said to taste better.

Saddleback tortoises. (Credit: Florilegius/Getty Images)

Santa Fe Island and Floreana Island, a popular destination for sailors, saw their giant tortoises disappear first. It was thought that all the tortoises on Pinta Island had gone extinct as well, but in 1972 an expedition discovered a single animal roaming the island alone. Dubbed Lonesome George, he was cared for lovingly by rangers and naturalists at the Charles Darwin Research Station in the Galápagos for the next four decades. Efforts to find a mate for George and continue the Pinta tortoise line were unsuccessful, and his death in 2012 was thought to mark the end of the species. George was more than 100 years old when he died, but his keepers had hoped he would live for several more decades; Galápagos tortoises can live up to 150 years.

Little tortoises with genes of the Floreana Island giant tortoise species in a breeding center at the Galapagos National Park in Santa Cruz Island. (Credit: RODRIGO BUENDIA/AFP/Getty Images)

Recent developments, however, suggest that Lonesome George may not in fact have been the last of his kind. Back in 2008, scientists tagged some 1, 600 giant tortoises found living near Wolf Volcano on Isabela Island in the Galápagos. When geneticists at Yale University analyzed blood samples taken from the tortoises in 2012, they discovered that 89 of the animals partly matched the genetic profile of the Floreana tortoise. (The full DNA profile of the Floreana had been obtained using museum samples.) Some even had genes suggesting that their parents were living purebred Floreanas, previously thought to have gone extinct long ago. In addition, 17 of the Wolf Volcano tortoises had significant amounts of Pinta DNA, meaning that some of George’s closest living relatives—maybe even his next of kin—still survived.

Scientists trace this stunning development to the actions of some whalers or other seafarers, who more than a century ago dumped the saddleback tortoises they didn’t need into Banks Bay, near Wolf Volcano. By extending their long necks and floating on their backs, the tortoises are believed to have made their way to shore, where they interbred with the domed tortoises on Isabela Island.

At the end of last month, an expedition run by the Galápagos National Park Service, including researchers from Yale University and the Galápagos Conservancy, returned to Wolf Volcano. As reported in the New York Times, the scientists combed a 20-square-mile area in nine three-person teams. They aimed to capture the tortoises with the most distinctive looking saddlebacks: shells that rise up in the middle (like saddles) to make room for the tortoises’ long necks. They hoped that such prominent saddlebacks would indicate the highest levels of Pinta or Floreana genes.

Of the 1, 600 tortoises tagged and blood-sampled in 2008, the scientists found seven, including a male and a female with Pinta genes and one male and four females with Floreana DNA. In all, the expedition turned up more than 100 tortoises with the same telltale saddleback shape as Lonesome George. Of these, 32 tortoises (21 females and 11 males) went to a breeding center on Santa Cruz Island. Each weighs between 100 and 300 pounds, and appear to be around 30 to 40 years of age, though a few may be much older. The scientists now plan to analyze each tortoise’s DNA and separate members of the two species. After identifying which have the least mixed ancestry, they can begin the breeding process.

Within five to 10 years, new tortoise populations could be released on Pinta and Floreana Islands, which would help restore the islands’ declining ecosystem. As Galápagos tortoises are so low to the ground, they serve an important role in moving seeds and nutrients around, which helps keep the soil healthy. Even more exciting is the possibility that in only a few generations, the scientists’ work could result in Pinta and Floreana tortoises with 95 percent of their ancestral genes, effectively reviving two species once lost to history.

Source: www.history.com

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